The present invention relates to a vacuum pump that is used as gas exhausting means for a process chamber or other closed chamber of, for example, a semiconductor manufacturing apparatus, a flat-panel display manufacturing apparatus, and a solar panel manufacturing apparatus. The present invention also relates to a rotor for the vacuum pump.
A thread groove-type vacuum pump disclosed in Japanese Patent Application Publication No. S63-75389 and a vacuum pump disclosed in Japanese Utility Model Application Publication No. H5-36094 are known as this type of vacuum pump. These vacuum pumps have a columnar or cylindrical rotary member and a stator member surrounding an outer circumference of the rotary member.
The thread groove-type vacuum pump disclosed in Japanese Patent Application Publication No. S63-75389 and the vacuum pump disclosed in Japanese Utility Model Application Publication No. H5-36094 employ a configuration in which a thread groove pump flow path is formed between the rotary member and the stator member and a configuration in which the rotary member is rotated to exhaust gas through the thread groove pump flow path, by, in case of Japanese Patent Application Publication No. S63-75389, forming a thread groove on an outer circumferential surface of the rotary member and, in case of Japanese Utility Model Application Publication No. H5-36094, forming a thread groove on an inner circumferential surface of the stator member.
According to these vacuum pumps configured as described in Japanese Patent Application Publication No. 563-75389 and Japanese Utility Model Application Publication No. H5-36094, an increase in the gap between the rotary member and the stator member is known to lower their pump performances significantly.
These vacuum pumps, therefore, are designed to prevent the lowering of the pump performances by making the gap between the rotary member and the stator member as narrow as possible in a way that the pumps can be operated safely without having these members come into contact with each other, the gap being set in consideration of thermal expansion and creep of the rotary member that are caused due to centrifugal force generated by rotation of the pumps, as well as variation in manufacture of these rotary and stator members.
Especially in order to set the gap as narrow as possible, in Japanese Patent Application Publication No. S63-75389, the inner circumference of the stator member is formed with a soft material, which is then brought into contact with the rotary member at initial running of the pump, to grind off the contact part therebetween. In Japanese Utility Model Application Publication No. H5-36094, on the other hand, the outer circumferential surface of the rotary member and the inner circumferential surface of the stator member are formed in a taper shape, and the stator member is designed to move in an axial direction of the pump in case of abnormality. In this manner, the rotary member and the stator member are prevented from coming into contact with each other.
The problem with Japanese Patent Application Publication No. S63-75389 is that the process grinding off the contact part between the stator member and the rotary member by making the inner circumference of the stator member contact with the rotary member at initial running of the pump can ruin the corrosion protection coatings of the inner circumference of the stator member and the outer circumference of the rotary member, resulting in a deterioration of the anti-corrosion characteristics of the internal structure of the pump. The problem with Japanese Utility Model Application Publication No. H5-36094, on the other hand, is that, in a case where a gap in a minimum size is formed, providing such a mechanism for moving the stator member in the axial direction of the vacuum pump makes the structure of the vacuum pump complicated.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background.